


can't breathe oxygen down in hell

by smudgythoughts



Category: Supernatural
Genre: Alternate Universe - Apocalypse, Angst, Castiel (Supernatural)'s Trenchcoat, Grief/Mourning, Happy Ending, M/M, Mixtape, POV Alternating, Post-Episode: s12e23 All Along the Watchtower
Language: English
Status: In-Progress
Published: 2017-05-23
Updated: 2017-06-05
Packaged: 2018-11-03 16:58:49
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,005
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10971501
Author URL: https://archiveofourown.org/users/smudgythoughts/pseuds/smudgythoughts
Summary: Cas isn’t dead. But he might as well be. He’s trapped in the apocalyptic world with no way out. The Castiel that came out of the portal and was killed by Lucifer was the “apocalyptic version.” Dean and Sam aren't aware of that.While Dean and Sam mourn over the deaths of Cas and Crowley, they also try to find a way to open a portal and go back after Mary. Meanwhile, Castiel, Mary, Bobby, and a few other friends are struggling to survive in a world of death and destruction.(Unfinished until further notice)





	1. Chapter 1

**Notes for the Chapter:**

> I read a couple metas about Castiel's whereabouts, and this idea _would not leave me_. Posting will be pretty irregular, but I promise this'll be done before Hellatus is over.

_Dean_

Castiel _couldn’t_ be dead. And yet there he was, lying on the cold ground, trench coat bunched around himself, a blackened image of his unfurled wings seared into the grass beneath him.

Dean kept waiting for Cas to be healed, for an angelic light to course through his body, for him to blink his too-blue eyes and say an astonished "Dean?" He would give Cas a tight hug, and things would be back to how they had been before. Well, maybe not exactly. Because, when Cas woke up - death was like a deep sleep, to the Winchesters - Dean planned on telling him exactly how he felt. Planned on telling him those three big words, and, if Cas consented, kiss him senseless, like Dean should've done years ago. But Cas didn't wake up. Just lied there, unmoving.

The effort to stand suddenly became too much. Dean fell down, knees scraping against the muddy ground. Sam ran over to the house, toward the light show behind him. Dean didn’t even notice, too focused on the fact that _his angel_ was dead.

Something in him broke, right there, kneeling in front of Cas’s cold, dead body, moonlight swamping over them. Dean broke in a way that forty years of living hell hadn’t done. It wasn't something that could ever be healed.

Dean looked over at the ground behind Cas. The angel blade that Lucifer had used to kill Cas was lying discarded in the dirt, discarded, still wet with Cas’s blood. Dean wasn’t even at peace with the knowledge that Lucifer was gone, trapped in an apocalyptic world. Because Mary was gone as well. Of fucking course she was. Since when did Sam and Dean get happy endings? Dean's chance of a happy ending had ended with the thrust of a knife through Cas's heart.

 _Sam_ , he reminded himself, _Sam_ was in trouble. It was what Dean always told himself to keep going, after John’s death, Jo and Ellen’s, Bobby’s, and the deaths of countless other friends and family. It was the one thing that forced Dean to carry on: keep care of Sammy. And he was trapped in the house with Lucifer Jr., a friggin’ Nephilim. 

Dean left Cas. For one of the first times in his life, he left Cas. It was the more difficult than all the times before.

 

Dean managed to heave to himself to the house, then up the stairs. An hour ago, Cas had healed his injured leg, but that did nothing to mend the broken shell of a body he’d become.

“Sam!” He called out as he made it to the landing of the stairs. His voice was breathless and hushed, like he’d run a mile with a bag of weights on his back. But he had, hadn’t he? The knowledge that Cas was gone was heavier than any weight.

He peeked into the nearest room. Kelly was laid out on the bed, hands folded over her chest, face peaceful. She was more at ease than she’d ever been while alive. It must have worked, then - Lucifer’s baby had been born. Sam was probably in danger, and Dean still hadn’t seen any sign of him.

“Sam!” He called out, louder than before. “Sammy!”

“Over here!” Sam’s voice came from down the hall. Dean allowed himself a moment to suck in a relieved breath, before heading off after his brother. 

When he entered the room, he was surprised to see Sam sitting on a bed with a blond, middle-aged man lounged on the chair across from him.

“Is this - is this him?” Dean asked his brother, looking over the man critically. He was naked, with a blue baby blanket folded respectfully over his legs to hide his junk. His light-colored hair was sitting sort of floppy on his head, and his blue eyes were looking at Dean curiously. There didn’t seem to be anything supernatural about him. Then his eyes flashed yellow and Dean let out a totally manly yelp.

“Yes. Meet Jack Kline, offspring of Lucifer,” Sam said, looking unworried about what he was saying.

Jack held out a hand, and Dean reached over and shook it. He kept a hand on his gun, though, because he didn’t trust the Nephilim yet. Though it wasn’t like a gun would do squat against Lucifer's fucking child.

When he pulled back his hand, Dean asked, “Wasn’t he ‘posed to be a few feet short, have chubby cheeks, and, I dunno, be a fucking _baby_?”

“It’s similar to the deal with Amara,” Sam explained. “He grew up quickly.”

“And do not worry,” the Nephilim finally spoke. His voice was high-pitched, words garbled, like he’d been deaf his whole life and this was his first effort to speak. “I do not share my father’s plans for world destruction.”

“Uh, good, that’s good,” Dean responded, still on edge. His gaze flickered to the door, then the window, calculating how long it would take him to get Sam out if the Nephilim suddenly went dark side.

“Look, Dean,” Sam said, voice on the edge of exasperated. “He has a bit of human in him as well, so just give him a chance.” At Dean’s disbelieving snort, he added, “And Cas trusted him.”

“Yeah, well, Cas put his faith into a lot of people he shouldn’t have.” _Like me_ , Dean thought bleakly.

“Where is Castiel?” Jack suddenly asked. “He is supposed to teach me about this world.”

Dean dropped his gaze, eyes trained on the floor. He swallowed over the lump in his throat. “He’s - he’s dead.” It hurt to stay those words out loud. Now it was _real_.

“Oh?” Jack said, face twisting into a frown. “That is a shame. I quite liked him.”

“Yeah, I liked him too,” Dean said, still downcast. “He didn’t deserve to go out like - like that.”

There was a long, painful silence.

“So what’s our plan, Captain?” Dean asked his brother. He was going for joking and lighthearted, but the words came out as serious and sad. Dean tried to smile to make up for it. He utterly failed.

Sam took pity on him. “We’ll held back to the Bunker, with Jack in tow.”

“And Cas?” Dean asked, voice small.

Sam looked away, mouth pressed into a frown, expression sad. “I suppose we’ll have to burn his body.” The words fell harsh and heavy.

“No,” Dean said, answer immediate. “No, then they’ll be no chance of his coming back.”

Sam gave him a small, pitying smile. “Dean, I don’t want to face this truth either, but Cas is gone,” he said softly, as if Dean was a scared animal he was comforting.

Dean looked away. He would hold onto his denial as long as possible, even if he didn’t quite believe it himself.

“So what’s our other option?” Sam demanded. “Bring his _body_ back to the Bunker?”

“Yes,” Dean retorted. 

Sam gave Dean another sad smile. Dean resisted the urge to huff at him angrily. He wasn’t a fucking charity case - he was taking Cas’s absence _just fine_. A wet tear trickled down his cheek. Dean wiped it away angrily. He was fucking fine.

“So, do you plan on taking Cas’s body home in the Impala?” Sam asked. “Dirty up the backseat?”

“No, I’ll - I’ll,” Dean hadn’t thought that far, “I’ll take him home in his truck.”

“So Jack and I will head back to the Bunker in _your_ Impala, and you’ll drive Cas’s truck with his body in the trunk?” Sam asked, astonished.

“Yep,” Dean confirmed. “Don’t get my baby in any accidents, alright? I’ll meet you at the Bunker.”

 

Dean was in the front seat of Cas's truck. He reached into the pocket, searching around for its keys, downright _flinching_ when his fingers brushed against something of a familiar shape. Dean pulled it out, dumbfounded to see a mixtape labeled ‘Dean’s top 13 Zepp TRAXX.’ It was the mixtape he’d given Cas what felt like ages ago. The tape in it was a little tangled, meaning that Cas had played it many, _many_ , times before.

A tear trickled down his face. Right in Cas’s stupid truck, with his stupid cassette tape in his hands, his stupid trench coat on the seat next to him, and his friggin’ _body_ in the back, Dean started crying.

He managed to keep it together while carrying Castiel's corpse - _God_ , it hurt to call it that - into the truck, with Sam's help. He managed to keep it together while waving goodbye to Sam. He managed to keep it together while carefully pulling off Castiel's trench coat and lumping it in the seat next to him. Yet all it took was a fucking mixtape to do him in.

He didn’t - _couldn’t_ \- stop crying for a full five minutes. The tears fell like rain, hard and heavy.

Dean finally took in a deep breath, chest rattling like a broken toy, face wet with tears. He turned the mixtape over in his hands, then slid it into the player. When _Stairway to Heaven_ started playing, he broke into sobs once again. Cas was an angel, and, because he had no soul, he would never get into heaven. There was no chance of Dean ever seeing Cas again, he was just _gone_. Just like that, a snap of someone’s fingers, a cruel turn off the track, Cas’s life was over. It wasn’t _fair_. It was as far from fair as it could possibly fucking be.

 _Sam_ , he reminded himself, _Sam_ was on his way to the Bunker, probably stricken by grief as well. Dean had to help him, couldn’t let his brother down like he’d let his angel down. He put in the keys and started up the car, beginning the long journey back to the Bunker. Led Zeppelin permeated the air as his tears dried on his face.

Several hours into the drive, when the sky had grown dark and the moon was hanging high in the sky, Dean stopped at a little motel somewhere in Idaho. He didn’t even get a room, just parked the truck in a parking lot and struggled to get some sleep in the front seat of Cas’s truck, snuggled into his trench coat.

He didn’t get a wink of sleep. No surprise there.


	2. Chapter 2

**Summary for the Chapter:**

> Castiel is trapped in the apocalyptic world with Mary. Then Lucifer arrives.

_Castiel_

Castiel was lying on the cold ground, trench coat bunched around himself like a discarded halo, the right side of his body pressed into the dirt. He struggled to his knees, then his feet, angel blade still grasped tightly in his hand.

 _Lucifer_ , Lucifer was the last thing Cas remembered. He’d been taking care of Kelly, preparing for the arrival of her child, when, out of the blue, Dean, Sam, and their mother showed up, with Lucifer at their heels.

Their plan had been to lure Lucifer into the rift of time and space, then pray Jack closed it off with the Winchesters on the right side. As there was no sign of Lucifer, the first part of the plan must have worked - one of the first times ever.

Cas struggled toward the portal, intend on helping his family. The Winchesters, not the angels, because the angels had stopped being his family the moment they tried to kickstart the Apocalypse.

Just as Cas was about to reach a hand out to touch the rift, he felt something stir low in his gut. He stumbled away from the orange light, hand curling instinctively over his stomach. It was nothing like the insistent, carnal urges he’d gotten while human. No, this was so much softer, reminding him of happy times from the past. The Winchesters wrapping their arms around him in a tight embrace. Being called _family_ without the words said in a tone of disgust. Dean pressing a handmade mixtape into his hands with a shy, “For when I’m not there.” The warm feeling crept up, skirting past his heart, eventually settling on the edge of his consciousness.

 _Home_ , he realized contentedly, _this is what home feels like_.

So Cas opened himself to the other entity, let it flood his senses as his eyes flashed a musty yellow.

When he blinked, eyes rich pools of blue once more, he only had one thought: kill Lucifer. He reached a confident hand out toward the rift, and was swept off to the other side, stomach lurching.

There he was. Lucifer. The Devil. Crowley’s limp body crumbling before him. Castiel stomped right toward Lucifer, angel blade raised defiantly.

He heard Dean yell out “Cas”, sounding a million miles away. Castiel forced his way past the Winchesters - those distractions - and toward Lucifer. Samuel pulled Dean back as the eldest brother called out “Cas!” repeatedly, in an increasingly insistent tone. Castiel ignored him. The rift let out a low noise, and, with a _whoosh_ , the Winchesters were gone.

Castiel stabbed the blade cleanly through Lucifer’s chest. The archangel let out a half-choked sound, his eyes glowing a faint red.

Lucifer's body lurched forward, as if he was about to fall down, before righting himself. He looked down at Castiel, red eyes cruel, as he pulled the angel blade out of his chest with a simple twist of his hand. Lucifer threw the blade somewhere on the dusty ground behind him.

Castiel could only stare at him in surprise, mouth half-open like a fish out of water.

Lucifer chuckled darkly. "Oh, _poor Cassie_. Your silly plan didn't work. I'm an archangel, remember? Your blade hurts about as much as a sewing needle."

Before Castiel could reply, Lucifer made a quick wave of his hand, and Castiel was thrown in the air by an invisible force. He was flung a few feet away, landing on the ground with a loud _crack_. If he hadn't been an angel, the fall would have killed him. Castiel let out a groan of pain, unable to find the strength to move.

Lucifer stalked closer to Castiel. Out of the corner of his eye, he noticed a figure behind Lucifer dart out toward the portal. The man beared a striking resemblance to Castiel himself, as he was wearing the same beige trench coat and blue tie. He was practically a spitting image of Castiel, with the same bedraggled dark hair, faint stubble, and blue eyes. Dean would have called the other man Castiel's doppelgänger. He must have been his version of the apocalyptic world.

Lucifer stopped right in front of Castiel, and the latter managed to keep his gaze fixed on the archangel. Castiel's doppelgänger disappeared in the rift to the other world. Lucifer didn’t even notice, too focused on reveling in his victory.

"You know what?" Lucifer said, lips pressing together into a mock-pout. "I don't think I'm going to kill you. Instead I'm going to leave you here in this apocalyptic world, without any hope of ever seeing your Winchester lackeys again."

Castiel tried to get to his feet, but only made it as far as his hands and knees. "No. I - I won't let you," he stuttered out weakly. Castiel couldn't let Lucifer leave before he was able to kill him.

" _Yeah_ , well, while you work on that, I have a world to burn to the ground. Bye!" He said chirpily, strolling off toward the rift.

Castiel made one final effort to get to his feet, but failed utterly, plopping back on his ass. "I'll stop you!" He yelled after Lucifer.

"Sorry, Cassie, I'm otherwise occupied. Next time buy me dinner first, and I'll think about it," Lucifer said with a fake smile, before he disappeared into the orange light of the rift.

Castiel’s mind suddenly cleared, the haze that had been clouding his thoughts dissipating like smoke. _The Winchesters_. The Winchesters were on the other side of the rift, and Cas had just let a deranged archangel go after them. Lucifer could be killing them that very second. Castiel shouldn’t even be capable of _feeling_ , but humanity seemed to have left a mark on him that would never fade. Cas still wasn’t sure if that was a good thing. Because it _hurt_ to feel - hurt like an angel blade digging into his chest, a clawed hand with a tight grip of his heart, a hurricane of dread building up inside him, close to climax.

There was still hope. A minuscule, microscopic, small amount of hope. If Cas could get to the rift in time, there was a chance that he could save his family. And if Cas had learned anything from the Winchesters, it was to not give up, even when everything seemed lost.

Bruised and broken, Cas got to his feet, slowly limping toward the portal, his left foot dragging against the dirt. Pins and needles prickled his legs, poison ivy and twisted vines, sprouting and spreading, but he kept going. For his family. For Dean.

He only made it a few painful steps when the rift let out a low noise, and two people tumbled onto the ground, as pliant as a pair of tossed out dice. The rift then hissed and spluttered out, like an overused light bulb, leaving no sign that it had ever been there in the first place.

It was Mary. She wore a green leather jacket and a wary frown, the latter fitting her better.

Cas allowed himself a small smile, ready to get out from behind his triangular-structure and greet her. But when he saw the other person with her, he froze.

It was Lucifer. He made his way to his feet, voice shrill, screaming a panicked, " _NOOO_!" If Cas hadn't known of the numerous people who took their last breaths because of him, he would have almost felt sorry for the Devil. The other universe was his home too. Mary stood up, eyes wide, a hand going to where her gun should've been.

The feeling from earlier built up inside Castiel, sweeping through him like a tidal wave, until he brought his gaze from Mary to Lucifer, once again gripped with the all-consuming desire to kill Lucifer, to eradicate him from this Earth. From all Earths.

**Notes for the Chapter:**

> And I hope I captured Lucifer's voice well - I'm not as familiar with writing him.


End file.
